A scanning electron microscope (SEM), a transmission electron microscope (TEM), etc. are used in order to observe a micro region of an object. Generally, in these devices, housings in which samples are arranged are vacuum-evacuated, sample environments are brought into vacuum states, and the samples are observed. However, biochemistry samples, liquid samples, etc. are damaged or changed in states by vacuum. On the other hand, demand for observation of such samples by the electron microscopes is greatly raised. In recent years, SEM devices capable of observing observation target samples under the atmospheric pressure, sample holding devices, etc. have been developed.
In principle, these devices are in principle configured to provide a diaphragm or a micro through-hole, through which an electron beam can pass, between an electron optical system and a sample, to thereby separate a space in vacuum state from a space in atmospheric pressure state. Any of the devices are common in point of providing the diaphragm between the sample and electron optical system.
For example, Patent Document 1 discloses an SEM in which an electron source side of an electron optical lens barrel is arranged downward and an objective lens side is arranged upward, and a diaphragm through which an electron beam can pass is provided via an O-ring on an electron-beam exit aperture at an end of the electron optical lens barrel.
According to the invention described in the Patent Document, an observation target sample is carried directly on the diaphragm, a primary electron beam is irradiated onto the lower surface of the sample, a reflected electron or a secondary electron is detected, and SEM observation is performed. The sample is held in a space defined by an annular member, installed around the diaphragm, and the diaphragm, and further is filled with liquid such as water.